A digital radio transmission system is known from technical specification (ETSI TS 101 980), having the title “digital radio mondiale (DRM); System Specification”, and published by the European Telecommunication Standards Institute in September, 2001, which, for instance, is transmitted on the usual AM frequencies, and, among other things, has a Service Description Channel (SDC) which is described on pages 63 to 78, as chapter 6.4. In the DRM system, the data are subdivided into SDC blocks and transmitted. Each block includes an indicator, called AFS index, and a data field by which useful data are transmittable, and a check word that is used for error detection and error correction. In this instance, the AFS index is a signless binary number between 0 and 15, which gives the number of the transmission of so-called super frames, which separate this SDC block from the next one having identical content, provided the 0 symbol is set in the identification field of the fast access channel. In this connection, the AFS index is supposed to be identical for all SDC blocks, and may be changed, for example, in response to a reconfiguration. The data field is subdivided into a variable number of data blocks (data entities). It may include an end marking in this case, as well as padding bits which fill up free fields. The length of this data field, in this instance, depends on the transmission mode selected, which determines the robustness of the transmission system. The check field, also called cyclic redundancy check (CRC), includes a 16-bit CRC data word which is calculated via the AFS index and the data field.
A protocol for analog radio transmission is known from ITU Recommendation BS. 706-2, having the title, “Data System in Monophonic AM Sound Broadcasting (AMDS)”, of February 1998, with which complementary data with respect to alternative frequencies are able to be transmitted, so that, in response to a serious deterioration in the quality of reception, switching is able to take place automatically to another reception frequency by the receiver.
In spite of the imminent introduction of DRM for digital radio transmission on long wave, middle wave and short wave, for a time, the same programs will be broadcast both in analog technology (AM) and in digital technology (DRM). Because of the limited number of channels, it may frequently be the case that an analog and a digital signal cannot both be transmitted in each frequency range. Especially on short wave, the various frequency ranges have different propagation ratios. Therefore, it may be necessary that a receiver that is first set to a DRM program and loses the signal there, has to change to another band in which, however, the program is only being transmitted in analog fashion. In order that it be able to refer additional possible alternative frequencies there, especially those on which digital transmission is being made, AMDS is used for the analog transmission.